Polymer/ceramic hybrid thin film dielectric

ABSTRACT

A conductor assembly including an electrically conductive material defining a longitudinal axis, a microporous membrane surrounding the electrically conductive material defining a series of pores, and a ceramic material within at least a first portion of the series of pores.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. patentapplication Ser. No. 16/536,755 filed on Aug. 9, 2019, which isincorporated herein by reference in its entirety.

BACKGROUND Technological Field

The present disclosure relates to dielectric device, and moreparticularly to polymer ceramic hybrid dielectric.

Description of Related Art

High-voltage power distribution systems require electrical insulatorsthat combine high dielectric strength with high thermal conductivity ina flexible (bendable) structure. High thermal conductivity yet lowdielectric constant, high dielectric strength combined with mechanicalflexibility, and the ability to form defect-free structures atreasonably large scale while maintaining their long-term integrity anddielectric properties even in high-humidity environments are alldesirable characteristics.

The conventional methods and systems have generally been consideredsatisfactory for their intended purpose. However, there is still a needin the art for a dielectric material having improved electrical andthermal conductivity. There also remains a need in the art for such amaterial and components that are economically viable. The presentdisclosure may provide a solution for at least one of these remainingchallenges.

SUMMARY

A conductor includes an electrically conductive material defining alongitudinal axis, a microporous membrane surrounding the electricallyconductive material defining a series of pores, and a ceramic materialwithin at least a first portion of the series of pores, and can furtherinclude a non-porous layer surrounding the microporous membrane. Asealant material can be located within at least a second portion of theseries of pores. The first portion of the series of pores issignificantly smaller than the second portion of the series of pores.

The microporous membrane can include a polymeric matrix and aspherulitic structure. At least a portion of the series of pores of themicroporous membrane can be aligned orthogonal to the longitudinal axis.The microporous membrane can include a thermoplastic fluoropolymermaterial, such as PEEK, PTFE or PVDF or a silicone material. The ceramicmaterial can includes a boron nitride or aluminum nitride.

A method of manufacturing an electrical conductor includes depositing amicroporous membrane over electrically conductive material such that aseries of pores are formed within the microporous membrane, filling atleast a first portion of the series of pores with a ceramic material,and filling at least a second portion of the series of pores with apolymeric electrically insulating sealant. Filling the first portion ofthe series of pores can include atomic layer deposition, which is plasmaenhanced. The method further including exposing the microporous membraneto a plasma mixture containing a ceramic precursor.

These and other features of the systems and methods of the subjectdisclosure will become more readily apparent to those skilled in the artfrom the following detailed description of the preferred embodimentstaken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

So that those skilled in the art to which the subject disclosureappertains will readily understand how to make and use the devices andmethods of the subject disclosure without undue experimentation,preferred embodiments thereof will be described in detail herein belowwith reference to certain figures, wherein:

FIG. 1 is a cut away view of a dielectric material, showing across-sectional view of the material of FIG. 1 along the transverseaxis; and

FIG. 2 is a cut away view of FIG. 1 , showing a cross-sectional view ofthe material of FIG. 1 along the longitudinal axis.

DETAILED DESCRIPTION

Reference will now be made to the drawings wherein like referencenumerals identify similar structural features or aspects of the subjectdisclosure. For purposes of explanation and illustration, and notlimitation, a partial view of an exemplary embodiment of a conductor inaccordance with the disclosure is shown in FIG. 1 and is designatedgenerally by reference character 100. Other embodiments of the materialin accordance with the disclosure, or aspects thereof, are provided inFIG. 2 , as will be described. The methods and systems of the disclosureoffer a unique approach to a hybrid material having a continuousthermally conductive ceramic phase within a flexible polymeric phase tothus improve thermal conductivity while maintaining electricalinsulation.

In particular, electrical insulators fall broadly into two materialscategories: polymeric and ceramic. Polymeric materials have theflexibility required to form around metal conduits and to withstandstresses due to bending and vibrations; however, they have very lowthermal conductivity. Certain electrically insulating ceramics have twoorders of magnitude higher thermal conductivity than polymers, but in amonolithic structure they are highly susceptible to stress cracking.Hence, a hybrid structure that combines the flexibility of a polymerinsulator with the thermal conductivity of a ceramic insulator enablessynergies towards these conflicting requirements better than eithermaterial class alone.

FIG. 1 shows a conductor assembly 100 an electrically conductivematerial 102 defining a longitudinal axis 104, a microporous membrane106 surrounding the electrically conductive material 102 defining aseries of pores 105, and a ceramic material 110, such as a heatconductive, electrically insulating inorganic fillers within at least aportion of the series of pores. The pores of the microporous membrane106 are aligned orthogonal to the longitudinal axis 104. Byincorporating the ceramic material 110 in the pores 105 of themicroporous membrane 106, heat transfer along the transverse directionis improved. A non-porous layer 108 surrounds the microporous membrane106. In one embodiment, the microporous membrane 106 includes apolymeric matrix of pores and a spherulitic structure. The microporousmembrane 106 includes a thermoplastic fluoropolymer material, such aspoly (ether ether ketone) a.k.a. PEEK, PTFE, or PVDF or a siliconematerial. It is beneficial to utilize the polymeric microporous membrane106 as a substrate as PEEK is capable of continuous use at 250° C.,which is more than 100° C. higher than PVDF, but has lower dielectricstrength; therefore, its use as the microporous matrix is targeted toapplications where maximizing thermal conductivity is more importantthan maximizing dielectric strength, whereas PVDF would be targeted toapplications where maximizing dielectric strength is most important.

The ceramic material includes a boron nitride or aluminum nitride. Thestructure maximizes heat transfer along the cross-direction, byincorporating heat-conductive, electrically insulating inorganicfillers, the ceramic material 110 in the microporous membrane 106. Asealant material 112 can be deposited within the series of pores into anarea between the pores 105, it may be desirable to fill the polymericmatrix void space only partly with the ceramic phase and back-fill theremaining void space with a polymeric electrically insulating sealant(e.g. silicone). At the early stage of ceramic deposition from the vaporphase, there is adequate void space in each of the pores such thatdeposition is essentially uniform along the axial direction. As thepores fill with the ceramic phase, precursor diffusion toward thelongitudinal axis of the conductor (i.e. farther from the outer surface)becomes progressively inhibited by the deposited ceramic layers,resulting in a relatively thicker ceramic layer near the entrance ofeach pore. By leaving a portion of the microporous membrane 106 open,the pores at the surface can remain uncovered. If pores at the surfaceare covered, the path of precursors toward the longitudinal axis wouldbe blocked and leave undesirable void spaces within the insulator.

A method of manufacturing the electrical conductor 100 is alsodisclosed. The method includes depositing a microporous membrane overelectrically conductive material such that a series of pores are formedwithin the microporous membrane, filling at least a first portion 111 ofthe series of pores with a ceramic material, and filling at least asecond portion 113 of the series of pores with a polymeric electricallyinsulating sealant, wherein filling the first portion of the series ofpores includes atomic layer deposition. Filling the pores formed withinthe microporous membrane with the ceramic done by atomic layerdeposition is required because a slurry-base method would result in theannealing temperature for the ceramic far exceeding the temperaturecapability of the polymer matrix and further the slurry volume would betoo large to fill voids with a concise amount of ceramic material.Atomic Layer Deposition (ALD) is a viable approach for allowing for thedeposition to be carried out at much lower temperatures and a morecontrolled deposition.

The methods and systems of the present disclosure, as described aboveand shown in the drawings, provide for a dielectric material withsuperior properties. While the apparatus and methods of the subjectdisclosure have been showing and described with reference toembodiments, those skilled in the art will readily appreciate thatchanges and/or modifications may be made thereto without departing fromthe spirit and score of the subject disclosure.

What is claimed is:
 1. A conductor assembly comprising: an electricallyconductive material defining a longitudinal axis; a microporous membranesurrounding the electrically conductive material defining a plurality ofpores; and a ceramic material within at least a first portion of theplurality of pores, wherein the pores of the microporous membrane arealigned orthogonal to the longitudinal axis and arrangedcircumferentially about the longitudinal axis configured to maximizeheat transfer in a plane transverse to the longitudinal axis.
 2. Theconductor assembly of claim 1, further comprising a non-porous layersurrounding the microporous membrane.
 3. The conductor assembly of claim1, further comprising a sealant material within at least a secondportion of the series of pores.
 4. The conductor assembly of claim 1,wherein the first portion of the series of pores is smaller than thesecond portion of the series of pores.
 5. The conductor assembly ofclaim 1, wherein the microporous membrane includes a polymeric matrix.6. The conductor assembly of claim 1, wherein the microporous membraneincludes a spherulitic structure.
 7. The conductor assembly of claim 1,wherein the microporous membrane includes a thermoplastic fluoropolymermaterial, or a silicone material.
 8. The conductor assembly of claim 7,wherein the thermoplastic material includes PEEK, PTFE or PVDF.
 9. Theconductor of claim 1, wherein the ceramic material includes a boronnitride or aluminum nitride.
 10. The conductor of claim 1, wherein theplurality of pores filled with the ceramic material is done by atomiclayer deposition.